Sertoli cells synthesize and secrete glycoproteins which interact with developing male germinal cells. It is the long-term goal of our research to ascertain the structure and function of these glycoproteins and thereby better define the role of the Sertoli cells in spermatogenesis. The experiments described in this proposal are designed to achieve three specific goals. First, a model has been proposed whereby testicular transferrin synthesized by Sertoli cells is instrumental in the transport of iron to selected stages of germinal cells. Experiments have been designed to assay for iron transport and to determine if transferrin mRNA is made by Sertoli cells in a cyclic manner during different stages of the spermatogenic wave. Second, the structure and function of the DAG-protein (dimeric acidic glycoprotein) complex will be examined in detail. The DAG-protein complex is the principal secreted glycoprotein of Sertoli cells, is also made by epididymal cells, and becomes a component of the sperm membrane. The subunit structure and the sugar composition of the DAG-protein complex will be analyzed by standard biochemical methods. Third, the relationship of impaired secretion of transferrin and DAG-protein by Sertoli cells to testicular dysfunction will be examined. The synthesis of transferrin mRNA and DAG-protein mRNA will be examined in rats and in cells obtained from rats which have been made cryptorchid or vitamin A deficient. The unique aspects of this proposed research include the use of cloned cDNA probes to assay for transferrin and DAG-protein mRNA and the isolation and purification of Sertoli cell secreted proteins by high-pressure liquid chromatography. The results from this research will provide important insights into the biochemistry of spermatogenesis and will give basic information relating to problems of male fertility and infertility.